1. Field of the Invention
The invention disclosed herein is concerned with the preparation of secondary alcohol mixtures which are enriched in C.sub.3 -C.sub.20 alkanols having hydroxy functionality in the 2-position. Such mixtures are prepared from olefinic compounds in the presence of carboxylic acids and particular zeolite catalysts.
2. Description of the Prior Art
Secondary alcohols can be prepared by hydrolysis of secondary alkyl carboxylate esters. The production of such alcohol precursors by reaction of carboxylic acids with olefins in the presence of Lewis Acid catalysts is known. However, the reaction results in the apparently indiscriminate addition of the carboxylate to either end of the olefin double bond, thereby giving rise to a mixture of structural isomers of the alkylcarboxylate product. Mineral acids (e.g. H.sub.2 SO.sub.4) are also reported to catalyze the reaction, but the result is much the same, i.e. non-selective addition of the carboxylic acid to either side of the carbon-carbon double bond. Trevillyan; U.S. Pat. No. 3,492,341; Issued Jan. 27, 1970 discloses preparation of alkyl carboxylate esters by reacting carboxylic acids with 1- or 2-monoolefins over a mordenite zeolite catalyst.
Prior to the present invention the only known method for producing commercially valuable secondary alcohol mixtures enriched in alcohols having the hydroxy group in the 2-position has been to utilize substantially pure, but expensive, alpha-olefins as the starting material. Reaction of carboxylic acids with internal or mixed olefins using the common acid catalysts necessitated physical separation of the isomeric and structural variants of the alkyl carboxylic product (e.g. by distillation) in order to isolate the desired .alpha.-methylalkyl carboxylate alcohol precursor. Subsequent hydrolysis of the .alpha.-methylalkylcarboxylates in the product resulted in almost stoichiometric conversion to the 2-alcohol.
The resulting secondary alcohols can be converted into nonionic detergents by reaction with ethylene oxide. It has been shown that detergents of this type which contain a high degree of hydroxy functionality in the 2-position, are superior in biodegradability to comparable ethoxylates having random hydroxy functional attachment up and down the carbon chain.
Detergent range higher alcohols and their derivatives are used in a wide variety of industrial and consumer products. In general, these materials are used either for their surface-active properties, or as a means of introducing a long chain moiety into a chemical compound. Only a small amount of detergent range alcohol is used as is, but rather most of it is used as derivatives such as poly(oxyalkylene) ethers, or esters of acids such as sulfuric acid, phosphoric acid, and mono- and dicarboxylic acids.
Surfactants derived from detergent range alcohols are widely used where emulsifying, dispersing, wetting, or detergent properties are desired. These surfactants are readily biodegradable and are finding increased use in low phosphate and nonphosphate detergents. The alcohols provide the starting material for all of the surfactant types: nonionics, anionics, cationics and zwitterionics. The alkyl sulfates, such as sodium dodecyl sulfate, C.sub.12 H.sub.25 OSO.sub.3 Na, are known for their cleaning ability and voluminous, stable foam. Alkyl sulfates derived from C.sub.12 through C.sub.15 linear alcohols are widely used in consumer products, for instance in toothpastes, hair shampoos, carpet shampoos, and light-duty household cleaners, whereas those derived from C.sub.16 and C.sub.18 linear alcohols are used in heavy-duty household detergents. Detergents having good foam stability have been reported from mixtures of C.sub.14, C.sub.16, and C.sub.18 linear alcohols. Minor amounts of unsulfated alcohol left in the alkyl sulfate detergents serve as foam stabilizers. The polyethoxylated alcohols, when sulfated and neutralized with a base such as sodium or ammonium hydroxide to give anionic surfactants, have wide application as light-duty dishwashing detergents and as part of the surfactant system of heavy-duty household liquid and granular detergents. These and other more specialized surfactants have a wide variety of industrial and household applications.
Cationic quaternary nitrogen surfactants of various types may be made by the condensation of tertiary amines with long chain alkyl halides, which are in turn obtained from the halogenation of a higher alcohol. Besides their use as surfactants, quaternary derivatives are widely used as disinfectants, bactericides, fungicides, antistatic agents, and textile softeners. Specialty phosphate ester surfactants and emulsifying agents are made by the reaction of phosphorous pentoxide and a detergent range alcohol. Other surfactants derived from these alcohols are alkyl amine oxides and alkyl glycerol sulfonates.
In another example of a surfactant application, dodecanol is used as a stabilizer for fire extinguishing foams. Hexadecanol and octadecanol are used in bar soaps and as antifoam agents in paper making and wastewater treatment, and dodecanol or higher alcohols are used to limit foaming in detergent compositions. The emulsion polymerization of various monomers is practiced in the presence of an alkyl sulfate surfactant, sometimes combined with free alcohol.